General Science Extension Activities Lesson 3

Buoyancy Activities

Test in Corn Syrup and Vegetable Oil – 01:15

Test the same objects from the lesson, but in corn syrup and vegetable oil. Buoyancy depends on the properties of both the object and the liquid.

Salt vs Fresh Water – 02:05

Make a cup or bowl of salt water (1 cup water : 3 Tbsp salt). Make an equal cup with fresh water. Test objects to see if they float: plastic building block, raw egg, grape, coin, shell, gummy candy. For an extra challenge, try a third cup with baking soda, cornstarch, or another powder mixed in.

Cartesian Diver – 04:53

There are many variations of this project. The simplest version uses a plastic bottle (a 2 L bottle is easier to see, but a smaller bottle works too). Fill it almost full with water. Insert a condiment packet (duck sauce is a common choice because it is clear and has a good air bubble). Fill the bottle completely with water and screw on the lid. Squeeze the bottle and the packet should sink. Release and it will pop back up. This is how fish swim bladders work — the pressure compresses the air bubble, making it denser so it sinks.